1. Field of the Invention
This invention relates to digital-to-analog and analog-to-digital devices; in particular, to systems which utilize the analog form as a common intermediary form between such devices. This invention is particularly applicable to devices such as Digital Video Disks (DVDs), High Definition Televisions (HDTVs), and the like, which utilize a digital form for processing, storing, or displaying the information, and utilize a common intermediary analogy form, such as NTSC or PAL, for communicating the information to each other.
2. Description of Related Art
FIG. 1 shows a system comprised of multiple components, with switching and selection means. Such a system may represent a home electronics center, a recording studio, a multi-media center, etc. The names of the components in the system of FIG. 1 are presented for illustrative purposes only. The components 101 through 108 are interconnected to each other via interconnections 111 through 119. Communications among the components via these interconnections will have a form and format such that each device can accurately receive the information content of these communications. Consider interconnection 115 and switch 105. Interconnection 115 may carry information from either component 106 or 107, via interconnections 116 or 117 respectively, in dependence upon the state of switch 105. Conventionally, to assure that device 104 is able to accurately transmit or receive information to or from the selected component, both components 106 and 107 operate using the same information format. The common information format also allows devices 106 and 107 to communicate with each other, also via switch 105.
Conventionally, commonly accepted formats are employed for the information exchange, so that the components may communicate independent of the particular vendors of the components, and independent of the form of the information utilized within the components. Because newer components must be compatible with legacy components to be marketable, the common formats are often those used before the advent of digital products. For example, if component 106 is a video recorder, component 107 is a video disk, and component 104 is a television, the format of the communications on interconnections 116 and 117 will be NTSC, PAL, or other common analog format. In this manner, via switch 105, components 104, 106, and 107 may communicate to each other as desired.
To effect a conversion to and from analog and digital form, standard digital encoders (DENCs) and decoders (DMSDs) have been developed. The digital encoders convert standard digital signals, such as MPEG encoded video, into standard analog signals, such as NTSC and PAL. The digital decoders, or video input processors, convert standard analog input, such as NTSC and PAL, into standard digital signals, such as MPEG encoded video. By incorporating such a digital encoder and digital decoder into a digital product, compatibility, via the analog standard, can be achieved with another component which conforms to the analog standard, independent of whether the other component is analog or digital. Similar interface components are available for converting audio signals to and from a standard digital form, such as AC-3 (a.k.a. "Dolby Digital"), DTS, S/PDIF, AES/EBU, ADAT, etc.
Digital components are often characterized as having higher quality than their analog counterparts. For example, CDs have the potential for much higher audio quality than cassettes; digitally recorded cassettes have the potential for higher quality than conventional analog cassettes. Similarly, DVDs and HDTVs have the potential for higher quality than VCRs and conventional televisions. These digital components may utilize newer digital formats, such as MPEG, CCIR 601 serial-D1, AC-3, S/PDIF, etc., for communicating digital data directly. Such direct communication minimizes the degradation caused by the conventional conversion of the digital signals to analog, and back to digital, between such digital devices. For example, if component 107 is a video disk, and component 104 is an MPEG-compatible television, the connection 118 could be an MPEG, digital, connection. Note, however, that even with a digital connection 108 for improved quality, components 104 and 107 must also contain an analog interconnection 115, 117 to maintain compatibility with legacy systems. If a device contains both an analog and digital interconnection capability, the selection between the format to be utilized is also required, typically requiring the user to manually select the specific source of the input to and output from each device.